Drainage and other trenches of various sizes and shapes are desirable for a number of applications. For example, manufacturing facilities typically require drainage systems that include trenches formed in the building floors to collect, remove, and/or recycle excess water or other liquids. These trenches may also be used as utility chases to provide temporary or permanent routing of electrical lines, pipes, conduits or the like below the level of the building floor. In addition, numerous outdoor industrial and commercial sites, such as parking lots, also require drainage systems, including trenches, to collect and direct rainwater and other liquids to underground storm sewers to prevent flooding and to decrease run-off. Similarly, roadways and the like may also require drainage systems, including trenches.
In the past, these trenches have generally been formed by first placing and securing a form of predetermined shape in a ditch that has previously been formed in the ground. A moldable trench forming composition, such as cementitious material, is then poured around the form and is allowed to set. Once the cementitious material has set, the form is removed from the resulting trench.
One type of form assembly used to define a trench includes a wooden form and strut structure. The wooden form includes a wooden frame which is covered with wooden sheets or planks to define a generally rectangular elongated trough. The wooden form is typically enclosed along its side and bottom faces, but may have an open top. Typically, a number of supporting wooden ribs are installed within the wooden form to increase the strength of the form so that it can withstand the relatively large pressures exerted by moldable trench forming compositions poured about it.
The wooden form is placed and secured within a preformed ditch. Cementitious material is typically poured up to the bottom face of the form and allowed to set in order to anchor the wooden form in the ditch. Then, additional cementitious material is poured between the earthen walls of the ditch and the wooden sides of the form. Once all of the cementitious material has set, the wooden form is disassembled and removed from the trench.
Wooden forms are generally formed of lumber having a relatively rough exterior texture. Correspondingly, the inside surface of the trench formed by the wooden form is relatively uneven which reduces the efficiency of the flow of liquid through the trench. In addition, the assembly and disassembly of the wooden forms is both costly and labor intensive. The relatively large cost and labor required for assembly and disassembly of the wooden forms is increased in the formation of long trenches, and even further increased in the formation of trenches having a pitched or slanted bottom surface to facilitate drainage.
Commercially significant methods for forming trenches, together with improved removable forms for forming trenches, are disclosed in U.S. Pat. No. 5,281,051, which is assigned to the assignee of the present invention and incorporated herein by reference. In advantageous embodiments thereof, inexpensive forms are employed to form trenches instead of using the wooden forms discussed above. The trench-forming assembly disclosed in U.S. Pat. No. 5,281,051 preferably includes opposing longitudinal frame members having a plurality of anchoring rods extending downwardly from the frame members. An elongated form body, preferably formed of relatively lightweight expanded polystyrene, includes aligned longitudinal slots in the opposed side walls for receiving the frame members. Horizontal portions of the frame members are secured within the longitudinal slots in the sidewalls of the form body during formation of the trench so that the frame members are held in alignment during the trench forming operation.
Preferably the assembled form and frame members are placed into a prepared ditch by suspending the assembly from its top, such as by one or more batter boards. Cementitious material is first poured around the bottom of the anchoring legs attached to the frame members and allowed to set in order to anchor the anchoring legs and, in turn, the frame members and the form within the ditch. Then more cementitious material is poured around the form body and allowed to set. Finally the form body is removed to expose the resulting trench and the properly aligned frame members. The removal of the form may be facilitated by a pair of slots extending upwardly into the form body from its bottom surface. By removing an upper portion of the form to access the slots as shown in U.S. Pat. No. 5,281,051, the form body can be more easily removed from the trench in several pieces.
Regardless of the fabrication technique, it is normally desirable to finish the trench with an elongated grate covering its open top in order to prevent people from unwittingly stepping in the open trench, to provide a smooth surface for vehicle travel, and/or to prevent relatively large objects from entering the trench and potentially blocking the flow of liquid therethrough. For a trench formed and described by U.S. Pat. No. 5,281,051, the grate is generally supported by a pair of spaced apart frame members which are set into and extend from the walls of the concrete trench. In order to stabilize the grate and to prevent the grate from rocking when weight, such as from a passing vehicle, is applied thereto, the frame members must be aligned in a common plane during the pouring and setting of the concrete about the form. If the frame members and, in turn, the grate are not properly aligned, the grate, the frame members and/or the cementitious trench itself may be damaged by the resulting movement of the grate. Accordingly, the alignment of the frame members in the moldable trench forming composition is important.
As shown by U.S. Pat. No. 5,348,421, which is assigned to the assignee of the present invention and incorporated herein by reference, the frame members may be connected by generally U-shaped members. While the U-shaped members generally maintain the frame members in position with respect to one another, the frame members are still able to move somewhat with respect to one another. Such relative movement is typically undesirable since it may adversely alter the relative alignment of the frame members such that the grate no longer sits evenly upon the rails. As such, one or more tie wires have been conventionally utilized to secure the frame members to the form. In this regard, the tie wires generally wrap about the opposed frame members so as to bring the frame members into snug contact with the opposite sides of the form. Once the cementitious material has set and the frame members are correspondingly affixed in position, the tie wires can be removed prior to removing the form to expose the resulting trench. And while tire wires are adequate for securing the frame members to the form, it is typically desirous to improve the method by which frame members are secured to the form.